The present invention relates to a device for dynamically measuring the bubble content of a flowing liquid. More particularly, the invention relates to a device provided in a conveyance passage for a flowing liquid, as may be used in the chemical or mechanical industries, or provided in a simple bypass for the conveyance passage, so that the bubble content of the flowing liquid and the bubble quantity of dissolved gas in the flowing liquid can be dynamically measured without extracting any of the liquid therefrom.
When a liquid such as a lubricating oil and a liquid containing a polymer, a surface active agent or the like flows through a passage with agitation, bubbles are likely to be produced in the liquid. The bubbles contained in the liquid are likely to cause various problems, such as an inaccurate measurement of the flow rate of the liquid, or, in the case that the liquid is a lubricating oil, a drop in the efficiency of operation of a hydraulic apparatus operated by the liquid and abnormal wear of the lubricated sliding surfaces of the machine. Although it is often necessary to dynamically, quickly and accurately measure the bubble content of a liquid, no appropriate measuring device has heretofore been available. Conventionally, a sample of the liquid has been extracted from a passage for the liquid and subjected to a gas chromatography or a static separation process. However, such procedures are time consuming, the bubbles in the liquid are likely to disappear, and it is difficult to accurately measure the bubble content of the liquid.
Accordingly, to overcome the above problems, a method and a device for dynamically measuring the bubble content of a flowing liquid without extracting any of the liquid from a passage were disclosed in U.S. Pat. No. 5,041,990. The device is installed in a conveyance passage of a bubble-containing liquid or in a bypass of the passage. The device includes a density sensor sensitive to the density of the bubble-containing liquid, a pressure sensor, a temperature sensor, a pressure calculation circuit, a temperature calculation circuit, a bubble content calculation circuit, a control panel, and a bubble content display panel. The density of the liquid, which changes depending on the bubble content of the liquid, is first measured. The pressure calculation circuit, the temperature calculation circuit, and the bubble content calculation circuit then carry out calculations in accordance with a predetermined formula and an instruction from the control panel to determine the bubble content of the flowing liquid at a standard pressure and a standard temperature. The bubble content determined in this manner is indicated on the bubble content display panel.
Although the bubble content of the liquid at high pressure can be measured by the method and device disclosed in the above-mentioned patent, there is still such a problem that it is difficult for the method and the device to dynamically measure the bubble content of the liquid at low pressure and the quantity of dissolved gas in the liquid.